This invention relates generally to means and methods for testing electrical surge arresters.
Many types of electrical equipment, particularly exteriorly located equipment such as that used in he telephone and communications industries, are particularly susceptible to damage by surges of high current like that associated with atmospheric lightning. To protect such equipment from electrical surges, arresters are often placed upon the equipment to shunt any such surges away therefrom.. A common type of surge arrester comprises a gas discharge tube which, upon ionization of the gas by the application thereto of high voltage, becomes conductive and thereby shunts the electrical surge arrester. Another form of surge arrester, which typically is used in the telephone industry, utilizes carbon blocks for such breakdown and bypass circuit switching purposes.
With the passage of time surge arresters of the type described may deteriorate and become unreliable. To insure the safety of the equipment it therefore becomes necessary and prudent periodically to test the surge arresters to insure that they are functioning properly by becoming conductive upon the application of voltages within a selected voltage range. Heretofore, surge arresters have typically been tested by the application of voltages thereto of increasing magnitudes until breakdown or firing of the surge arrester occurs. Once breakdown occurs the application of voltage is continued to deflect a moving coil over a scale to enable a reading to be observed by a tester. Once this reading is visually made voltage is removed from the arrester.
Though prior art test devices of the type described have provided basic means for testing surge arresters, they have not been without distinct disadvantage. For example, in order to cause their moving coil to stabilize for visual readings they have required repetitive firings of the arresters under test. Such repetitive firings can themselves be destructive of the arrester. This is particularly true in the communications industry in which the arresters typically utilize carbon blocks. Furthermore, since the tester moving coils inherently reflect voltages indicative of residual ionization present during repetitive firing, they typically indicate a voltage somewhat lower than that of actual firing voltages. The devices have thus been generally inaccurate, often injurious to the very devices they are designed to test, and susceptible to human error in visually reading the indicated firing voltages.
Accordingly, it is a general object of the present invention to provide improved means and methods for testing electrical surge arresters.
More specifically, it is an object of the present invention to provide means and methods for testing surge arresters which require but a single firing of the arrester during test operations.
Another object of the invention is to provide means and methods for testing surge arresters of improved accuracy over those of the prior art.
Another object of the invention is to provide means and methods for testing surge arresters that are capable of digitally displaying firing voltages.
Yet another object of the invention is to provide means and methods for testing surge arresters employing portable power supplies and which include means for self-testing the tester's own power supply.